Outcomes of Single-Level Lumbar Fusion in Osteoporotic Patients on Bisphosphonate vs Anabolic Pharmacotherapy: A Propensity-Matched Retrospective Cohort Analysis

Introduction: Osteoporosis increases the risk of complications in spine surgery, but the impact of preoperative bisphosphonate and anabolic pharmacotherapy on fusion outcomes remains unclear. This retrospective cohort study aims to assess how osteoporosis affects single-level lumbar fusions and compare the efficacy of preoperative osteoporosis medications on postoperative outcomes.

Methods: The TriNetX database was queried for patients (≥18 years) who underwent single-level lumbar fusion. Patients were divided into two groups: those with pharmacologically untreated osteoporosis before surgery (n = 10,974) and those without osteoporosis (n = 153,686). The cohorts were propensity matched demographics and comorbidities, resulting in two groups of 10,842 patients each. Then, two groups of patients with osteoporosis who underwent single-level lumbar fusion were compared. The first group (n=3,659) was prescribed bisphosphonates (Zoledronic Acid, Ibandronate, Alendronate) preoperatively, while the second group (n=560) was prescribed anabolic drugs (Romosozumab, Teriparatide, Abaloparatide) preoperatively. These groups were also propensity matched for demographics and comorbidities, resulting in matched cohorts of 558 patients each. In each comparison, 2-year postoperative medical and surgical outcomes were analyzed. Risk difference, relative risk, and odds ratio were calculated for each outcome. Statistical significance was considered p< 0.05.

Results: There was a significantly higher 2-year risk of revision surgery (p < 0.0001), hardware failure (p < 0.0001), and lumbar vertebral compression fracture (p < 0.0001) in patients with pharmacologically untreated osteoporosis undergoing single-level lumbar fusion. Patients with osteoporosis that were preoperatively prescribed bisphosphonate pharmacotherapy prior to single-level lumbar fusion had a significantly higher 2-year risk of pseudoarthrosis (p=0.045) compared to patients using anabolic agents in the same timeframe.

Conclusion : There is a strong association between pharmacologically untreated osteoporosis and postoperative complications following single-level lumbar fusion, and anabolic pharmacotherapy, compared to bisphosphonates pharmacotherapy, prior to surgery may be protective against long-term surgical complications.